1. Field of the Invention
The present invention relates to an electric vacuum cleaner and, more particularly, to an electric vacuum cleaner in which input to an electric blower is automatically controlled in response to operating conditions of a floor nozzle.
2. Description of the Background Art
Conventionally, a technique has been proposed for improving an electric vacuum cleaner by varying the power supplied to an electric blower in accordance with the magnitude of the suction and the amount of dust collected in a dust collecting chamber. Such a conventional technique includes a pressure detecting device provided in an air inlet passage between an electric blower and a filter. The pressure in the dust collecting chamber measured by the pressure detecting device, and power to the electric blower is varied according to the detected pressure value. An electric vacuum cleaner using such a technique is disclosed, for example, in Japanese Patent Laying-Open No. 57-75623 (1982).
In such a conventional technique, however, input to the electric blower is varied only with the pressure in the dust collecting chamber, and it is difficult to optimize control to actual operating conditions of a floor nozzle performing dust collection and a floor surface subject to dust collection.
For example, in the case of the surface of a floor of board floor, a suction port of the electric vacuum cleaner tends to cling to the floor surface. Once it clings to the floor, the pressure in an air inlet passage is lowered. In such a case, input to the electric blower is increased in accordance with the decrease of to make the suction still greater, so that the suction port clings more strongly to the floor surface in the above-described conventional technique. As described above, in power to the conventional electric vacuum cleaner, control of the electric blower adapted to actual conditions of the floor nozzle and the floor surface is not performed, and operation of the vacuum cleaner is not improved.
Another approach is disclosed in Japanese Patent Laying-Open No. 64-52430 (1989), for example, in which suction power that varies with actual conditions of a floor nozzle and a floor surface is realized by sensing a change in electric current in a driving motor of a dust collecting rotary brush provided in a floor nozzle of an electric vacuum cleaner and automatically controlling power to an electric blower on the basis of the sensed current.
However, during normal cleaning, a variation in the electric current in the motor driving the rotary brush is extremely small; little change occurs in the average electric current. Therefore, it is difficult to control the electric blower precisely in accordance with actual conditions of the floor nozzle and the floor surface by controlling only power to the electric blower in proportion to the current in the driving motor of the rotary brush, as in the case of the above-described conventional technique.
Another electric vacuum cleaner is disclosed in Japanese Patent Laying-Open No. 3-26223 (1991), for example, in which fuzzy inference is performed on the speed of a floor nozzle's motion and the amount of dust in the sucked air, and suction power is controlled on the basis of the result.
However, in this electric vacuum cleaner, the speed of the floor nozzle is measured only by the of rotation of a roller attached to the floor nozzle; the sliding of the floor nozzle is not considered. Therefore, the actual conditions of use of the floor nozzle are not sufficiently reflected in the control of the suction.